Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$78.77	4.278%	$82.1398	$82.14	$82.15	$82.10
Purchase #2	$77.67	4.519%	$81.1799	$81.18	$81.20	$81.20
Purchase #3	$92.49	8.376%	$100.237	$100.24	$100.25	$100.20
Purchase #4	$107.97	3.264%	$111.4941	$111.49	$111.50	$111.50
Purchase #5	$157.89	6.479%	$168.1197	$168.12	$168.10	$168.10
Purchase #6	$33.59	10.417%	$37.0891	$37.09	$37.10	$37.10
Purchase #7	$137.74	11.837%	$154.0443	$154.04	$154.05	$154.00
7 purchase totals =	$686.12		$734.3039	$734.30	$734.35	$734.20